Various catalysts which substitute fluorine atoms for chlorine atoms have been proposed for use in gaseous phase reactions. Frequently, these catalysts are oxides or halides of chromium, aluminum, cobalt, iron, titanium, nickel, copper, palladium or zirconium; which may be supported on active carbon or alumina. French Pat. No. 720,474 and its Certificate of Addition No. 43.972 teach gaseous phase fluorination of hydrocarbons containing a halogen other than fluorine, by metallic halide catalysts.
U.S. Pat. No. 2,110,369 discloses the fluorination of C.sub.1 to C.sub.3 halohydrocarbons over catalysts having a chromium halide base deposited on coke or active carbon.
U.S. Pat. No. 2,458,551 describes a catalyst prepared by impregnating active carbon with chromium trichloride and subsequently heating the product with hydrofluoric acid under anhydrous conditions.
To obtain trichlorotrifluoroethane and dichlorotetrafluoroethane with small amounts os asymmetric isomers, French Pat. No. 2.000.688 teaches the use of pure chromium trifluoride or chromium trifluoride supported on wood charcoal, petroleum coke or coal carbon as a catalyst for the reaction of tetrachloroethylene with chlorine and hydrofluoric acid.
These commonly used chromium halide catalysts deposited on carbon supports are basically suitable for gaseous phase fluorination of chloroalkanes or chlorofluoroalkanes in fixed bed reactor systems. In fluidized bed reactors, which require regular-shaped particles and homogeneous granulometry, the prior art catalysts are inadequate and inefficient for use in fluorination processes. Simple grinding of the catalysts, followed by shifting for the selection of suitable-sized particles provides irregularly-shaped grains which are not suitable for use in fluidized bed reactors. Consequently, their use leads to a significant loss of the catalyst, which necessitates recharging the reactor at various intervals during the process.
The prior art catalysts often demonstrate at least one of the following disadvantages:
low rate of conversion of hydrofluoric acid PA0 low productivity PA0 low selectivity PA0 low activity in the fluorination of chlorinated derivatives other than chlorocarbons, and especially in the fluorination of chlorinated nitriles.